1. İs tanbul University Faculty of Engineering Hacer DÜZEN a, Halil Murat ÖZLER b a,b İstanbul University, Faculty of Engineering, Department of Geological Engineering, 34825, Avcılar, İstanbul-Turkey (hcrduzen@gmail.com), (ozlerhm@istanbul.edu.tr) Acknowledgements The authors acknowledge the support of İstanbul University Research Fund (Project Number: 36796 ) and thanks to İstanbul University Research Fund. Introduction Muradiye-Çaldıran geothermal field, which includes the thermal waters of Ayrancılar (Çaldıran), Buğulukaynak (Çaldıran) and other little springs in Muradiye and Çaldıran is located in the NW- SE and NE-SW trending Muradiye-Çaldıran basin in the eastern part of Turkey (Fig. 1). The aim of this study is investigating of hydrogeological and hydrogeochemical properties of Muradiye-Çaldıran geothermal field. So, thermal water samples from the study area were collected from 8 springs (samples 15CA, 21CA, 29CB, 27CK, 28CB, 2MO, 8MU, 10MY ) and 1 mineralized water spring (sample 32CE ). Cold water samples from the study area were collected from 25 points and 11 of them from well (samples 1MO, 3MK, 7MU, 11M, 17CY, 22CY, 24CK, 26CK, 33CD, 35 CH, 36CA) and 14 of them from springs (samples 5MKS, 6MTPZ, 9MB, 12M, 13CA, 16CK, 18CY, 19CA, 20CY, 23CK, 25 CK, 30CS, 31 CE, 34CH). There are 3 rock types as hydrogeological. Permeable rocks are alluviums, limestones, carbonates and marbles. Semi-permeable rocks are debris rocks and impermeable rocks are basalt, tuff-basalt, basaltic tuff etc. Groundwater levels were determined and direction of groundwater levels are NW in Çaldıran plain and W-SW in Muradiye (Fig. 2). Discussions & Conclusions Most of the thermal waters discharge along the NW–SE trending faults that form the Muradiye-Çaldıran basin. The circulation of thermal waters is closely related to major fault and fractured zones. There are 3 rock types including permeable, semi-permeable and impermeable in the Muradiye-Çaldıran field as hydrogeological. Permeable rocks are alluviums, limestones, carbonates and marbles. According to geophysical studies, thickness of alluviums are nearly 25 meters and volcanic rocks nearly 120 meters and thickness of metamorphic series is not known. A little geothermal activity zone with low enthalpy was detected in Çaldıran-Ayrancılar geothermal field. Thermal and cold waters from the study area can be divided into 3 distinct types. Most of water samples (20 point) are CaHCO 3 type. MgHCO 3 (8 point) and NaHCO 3 (5 point) type waters form the second and third groups. Only one of the sample is Ca-SO 4. Groundwaters are fresh waters and dominant water types are Ca–HCO 3 and Mg-HCO 3. Chemical elements indicate an origin controlled by the dissolution of carbonate rocks. As a result of the evaluation, waters in study area include HCO 3 +CO 3 at the high levels, Cl level is low at the most of the samples and only a few samples have high chloride. Water quality assessment shows that in general, the waters are suitable for potable, domestic and irrigation purposes. Ionic concentration, pH and EC parameters in Muradiye-Çaldıran province suggest that climate and lithological units are major controlling factors of groundwater chemistry. Results 1. Geophysical Studies The purpose of these studies was investigating geothermal energy resources and detecting distribution of aquifer and layers. Gravity and electric-rezistivity methods were applied to the Çaldıran-Ayrancılar geothermal field which is center of the study area and vertical electrical drilling applied at the 34 points by using Schlumberger electrot arrangement. A rezistivity map was prepared by using lowest rezistivity values at each point purpose of geothermal energy activity in Figure 3. So a little geothermal activity zone with low enthalpy was detected. Also aquifer thickness was measured in Muradiye-Çaldıran field. These geophysical studies were carried out for the purpose of detecting distribution of aquifer and layers in the general of the field, thickness of alluviums are nearly 25 meters and volcanic rocks nearly 120 meters and thickness of metamorphic series is not known. Material and Methods Temperature, electrical conductivity and pH values were measured at spring and wellhead conditions. The remaining chemical constituents and some trace elements were analyzed in the Canada ACME Laboratories by using ICP-MS method and CO3 (carbonate), HCO3 (bicarbonate), SO4 (sulfate) and F (fluorid) were analyzed by using chemical cuvette tests. INVESTIGATION OF HYDROGEOLOGICAL AND HYDROGEOCHEMICAL PROPERTIES OF MURADIYE-ÇALDIRAN (VAN) GEOTHERMAL FIELD, EASTERN TURKEY 2. Water Chemistry Some GIS (Geographic Information Systems) based computer programs were used to evaluate mineral speciation and to construct the diagrams. Durov diagram were showed in Figure 4 for all sample points (34 point) including cold waters and thermal and mineralized waters. It shows that most of water samples (20 point) are CaHCO 3 type, 8 points show MgHCO 3 and 5 points show NaHCO 3 water type (Table 1 and Fig.4). Generally, TDS values are between 0 and 500 mg/l at the sample points. pH values are between 6.8 and 8.8. pH values show that many samples are 8 and upper. Also EC values were showed in pH and temperature maps at the left (Fig. 5). Temperature map shows that NW of the study area is hotter than SE. It is related to faults in the region. NOpHECTCaMgNaKHC03S04CICO3FBWater (μs/cm)(oC)mg/l µg/LType 1MO7.89146522.1170.6395.3565.654.41498.912914901.58553Ca-HCO3 2MO7.7530223.963.028.798.121.14243.462.1100.9350Ca-HCO3 3MK7.6963621.669.9642.5145.4310.69547.6661101.44839Mg-HCO3 5MKŞ7.6160826.879.9935.6117.247.71425.965.2201.42171Ca-HCO3 6MTPZ8.0034423.354.2213.3110.432.03456.364.5201.2462Ca-HCO3 7MU8.0555614.590.8928.3917.612.98243.466.3901.18130Ca-HCO3 8MU7.8256820.293.4025.1125.751.93425.964.61301.39175Ca-HCO3 9MB8.0826723.735.489.9414.871.53182.564.8<101.01245Ca-HCO3 10MY8.0514326.715.255.274.240.85121.761.8<100.8913Ca-HCO3 11M7.9654316.568.5322.1449.096.90407.662.4601.7549Ca-HCO3 12M8.1036620.545.1013.3319.8926.57231.266.61201.37135Ca-HCO3 13ÇA8.1218030.225.224.0313.232.85194.764.4<101.839Ca-HCO3 15ÇA7.74342034.7117.3026.00724.00195.0011863.8179*04.3559363Na-HCO3 16ÇK8.0243116.467.1819.8821.486.59400.965.1201.45347Ca-HCO3 17ÇY8.4132016.443.789.3816.784.79291.466.2301.23104Ca-HCO3 18ÇY7.65508.811.5110.67123.2512.91785.463504.34427Na-HCO3 19ÇA7.55101711.4710.80121.7112.67770.863503.94413Na-HCO3 20ÇY8.3972520.399.5445.7021.081.5493.7644501.2156Ca-HCO3 21ÇA8.8113620.218.262.0911.980.6640.266<100.9443Ca-HCO3 22ÇY8.677111872.6167.8813.321.2978.5625100.9793Mg-HCO3 23ÇK8.613471753.9414.7315.665.64343.164500.9476Ca-HCO3 24ÇK8.07103.621.311.940.4115.950.3923.760.3<100.2233Na-HCO3 25ÇK8.7988.92310.201.149.190.5332.261<100.9234Ca-HCO3 26ÇK7.59193818.1164.29134.60144.3373.154450.412116100.962104Mg-HCO3 27ÇK7.43169620.7168.00104.83167.8948.422945.966.44800.858717Mg-HCO3 28ÇB7.29115533.593.5979.2598.8626.721625.663.81601.192082Mg-HCO3 29ÇB8.426020.77.461.873.241.4789.459.9<100.8954Ca-SO4 30ÇS8.76145.913.718.587.157.381.0060.865<100.4865Ca-HCO3 31ÇE7.3020215.428.628.7912.264.47272.062.2<100.9276Ca-HCO3 32ÇE6.849619.145.4140.8431.209.83598.158.4<101.36113Mg-HCO3 33ÇD8.1261018.491.4917.8716.1233.432033.970.25701.3472Ca-HCO3 34ÇH7.9850324.511.7411.05124.9212.74775.159504.16453Na-HCO3 35ÇH8.38197913.786.61148.27266.7319.601192.519916603.231148Mg-HCO3 36ÇA8.51139514.581.40101.98143.6871.064323.312811302.82814Mg-HCO3 Figure 1. Location map of study area. Figure 3. Çaldıran-Ayrancılar lowest rezistivity values at 34 points. Table 1. Chemical analyses of thermal waters and cold ground waters (EC: electrical conductivity) Figure 2. Hydrogeological map of the study area. Figure 5. EC values in pH and temperature maps.Figure 4. Durov diagram of all sample points in study area.